The objective of this research project is to identify and characterize cell surface glycoproteins of mouse lymphocytes with a long-term goal of understanding lymphocyte differentiation and function. Work has continued on preparing monoclonal antibodies against cell surface molecules that may be of functional significance. One murine monoclonal antibody, designated 140/25, has been obtained that reacts with a clonotypic determinant of the T-cell receptor expressed on a human T leukemic cell line, HPB-MLT. The monoclonal antibody has been used to purify the putative T-cell receptor from HPB-MLT cells, and mouse antisera have been obtained that react with framework determinants of the human T-cell receptor. Another murine monoclonal antibody has been obtained against the human IL-2 receptor by immunization of mice with the human T-cell line, HUT 102; and the expression of the IL-2 receptor on human leukemic cell lines has been studied. Treatment of some human T-leukemic cell lines with phorbol ester induces the expression of IL-2 receptors that differ in apparent molecular weight from those expressed upon HUT 102 cells. The source of heterogeneity appears to be due to post-translational processing of the receptor. Incubation of cells with phorbol ester also induced the rapid phosphorylation of serine and threonine residues on the IL-2 receptor from HUT 102 cells. This phosphorylation may be mediated by the Ca[unreadable]2+[unreadable] and phospholipid-dependent protein kinase C. (LB)